Identity crisis and incomprehensible T&C

I bought a SIM today in order to take advantage of the headline offer of "International calls from 1p/min".

The identity crisis: The packaging says O2, the T&C says Telefonica UK and the phone says BT Cellnet!

The T&C: talks about having to top up £15/month to "keep your free monthly allowance", but I don't see International calls as being within any "allowances", they are PAYG. Does this mean I can load £15 and use it at my leisure (over many months) while using this SIM only to make International calls?
Roland Perry